A liquid crystal display device employing a liquid crystal material, a TN (twisted nematic) mode liquid crystal display device is in practical use. In such a mode, light switching is carried out employing optical rotation property of a liquid crystal, and a liquid crystal display device in this mode requires use of a polarizing plate. However, use of a polarizing plate lowers the light utilization efficiency.
As a liquid crystal display device which achieves a high light utilization efficiency without using a polarizing plate, a liquid crystal display device in which switching is conducted between a transmission state (also called a transparent state) and a scattering state of a liquid crystal may be mentioned, and a liquid crystal display device employing a polymer dispersed liquid crystal (PDLC) or a polymer network liquid crystal (PNLC) is commonly known.
A liquid crystal display device employing such a liquid crystal is a liquid crystal display device comprising a liquid crystal layer between a pair of substrates provided with an electrode, formed via a step of disposing a liquid crystal composition containing a polymerizable compound which undergoes polymerization by ultraviolet rays between the pair of substrates and curing the liquid crystal composition in such a state that the liquid crystal composition partly or entirely shows liquid crystallinity, to form the liquid crystal layer, that is, a cured product composite (for example, a polymer network) of a liquid crystal and the polymerizable compound. And, in such a liquid crystal display device, the transmission state and the scattering state of the liquid crystal are controlled by voltage application.
A conventional liquid crystal display device employing PDLC or PNLC is in a cloudy (scattering) state when no voltage is applied since liquid crystal molecules are randomly aligned, and is in a transmission state when a voltage is applied since liquid crystal molecules are aligned in an electric field direction, whereby light is transmitted (such a liquid crystal display device controlling the transmission and scattering is also called a normal device). However, in a normal device, it is necessary to always apply a voltage in order to obtain a transmission state, and accordingly when it is used for an application which is mainly used in a transparent state, for example, when used for window glass, the electrical power consumption tends to be large.
Contrary to the normal device, a reverse liquid crystal display device employing PDLC, which is in a transmission state when no voltage is applied and is in a scattering state when a voltage is applied (also called a reverse device) has been reported (Patent Documents 1 and 2).